Increased demand and availability of mobile Internet services will create challenges for network operators and service providers due to the rising cost of the infrastructure. Large number of base transceiver stations (BTS) are needed to support the new technologies and to satisfy the capacity demand of the advanced services.
The Open Base Station Architecture Initiative (OBSAI) is an organization that aims to create a set of open specifications for the base station architecture. OBSAI has defined a modular base station architecture and detailed specifications for the interfaces between the modules. This architecture is depicted in FIG. 1. The base station in FIG. 1 includes a transport module 100 providing adaptation between external network interfaces and standard BTS internal interfaces. The processing module 102 provides baseband processing for the air interface and the radio module 104 provides radio frequency (RF) transceivers and conversion between digital baseband signals and analogue RF signals. Function module 106 includes functionality needed by the radio module. The control module 108 provides control processing of the base station. The open interfaces defined by OBSAI are shown in FIG. 1 by reference points RP1, RP2 and RP3. RP1 interchanges control, such as status, alarm and synchronization data. RP2 interchanges user data between the transport module and the processing module. RP3 interchanges formatted air interface user data and fast control data between the base band module and the radio module.
FIG. 2 illustrates one prior art base station topology, a star topology, for implementing the baseband module. FIG. 2 also shows the external interface 214 between the baseband module 202 and the RF module 204. The baseband module 202 includes a number of baseband devices 222A to 222D (indicated by F1 to F4) and a routing device 220 (indicated by O). The routing device is responsible for distributing/collecting all data to/from the baseband devices via the internal interfaces 224A to 224D.
In FIG. 2, the interfaces can include at least one OBSAI RP3 interfaces, for instance. As shown by FIG. 2, the data transfer capacity of the external interface and all the internal interfaces 224A to 224D is “N*RP3” (only data rate of 224A is shown in the figure), where N refers to the number of sub-interfaces and RP3 to the type of interface. In the case of RP3, the smallest data rate is 768 Mbps. The star topology has the disadvantage that an expensive routing device is needed.
Another prior art topology avoiding the use of a separate routing device is shown in FIG. 3. In this so-called daisy chain topology, the baseband devices 322A to 322D are arranged in a chain and the baseband device 322A is directly connected to an external interface 314. The number of interfaces (N) and the data rate of the baseband internal interfaces 324A to 324C is the same as in the external connections. In spite of the advantages over the star topology, the daisy-chain topology still suffers from a large number of interfaces per baseband device.